Q: Time Machine: External USB icon DOES NOT change to green Time Machine icon

thanks this worked for me too

Another trick is to relaunch Finder (hold alt+right click on Finder icon). Green icon restored.

I have found a simple fix to get the Time Machine to show green.  Simply go to force quit and select finder and click relaunch.  When it comes back up it will be green.  I have a Mac Book Pro and I Mac that was having this problem.  It has worked every time. Give it a try, Hope it works for you.

Thanks for that simple solution.  Worked fine 

Thanks a lot Josué... Finally I've fixed it!!!

To Jeffrey Drood (and all others who say "'this' helped me..."): What is, BY FAR, the most straight forward solution? What solution helped you? Many ideas are mentioned in this thread.

Context, please!

Finder->Preferences->General->de-select "External Disks" and then re-select it worked for me.

Thank you.

IlDavo, I had this same problem - and I guess it irked me more than it should have, lol. I simply did what geraldfromwichita did and the problem literally was solved in five seconds. Click on your desktop, open "Force Quit" (hold down the alt, command, esc key) and hit "Relaunch." My WD "My Passport for Mac" orange icon immediately turned to the proper Time Machine green icon. You gotta love it.

Thank you!!

This always use to annoy me but I seem to have found a tried and tested method that always fixes the issue. Whilst in Finder select the 'view' menu and then 'show view options'. Then select / deselect 'show icon preview'. I think upon each restart / update it pre-caches the Time Machine icon into memory and by selecting / deselecting the icon preview refreshes the icon. I hope this works.

I have this same issue. I just updated to El Capitan And I used the methods to get the icon to be green. But this happens every time I start up my  computer. do I have to go through this procedure EVERY DAY?

I haven't seen the green icon now in a week. But reading through this thread I realize this is because it's a new backup drive, and Time Machine hasn't finished it's first run yet. Every day I log on to work, it copies a few more gb during the day, then I log off.  I am guessing now that the icon will "stick" once it has completed it's first backup. It's darn slow about it though.